<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8" />
    <title>鼠标绘制线条</title>
    <style>
        body {
            margin: 0;
            overflow: hidden;
        }

        #canvas {
            background-color: antiquewhite;
        }
    </style>
</head>

<body>
<canvas id="canvas"></canvas>
<!-- 顶点着色器 -->
<script id="vertexShader" type="x-shader/x-vertex">
    attribute vec4 a_Position;
    void main(){
        gl_Position=a_Position;
        gl_PointSize=20.0;
    }
  </script>
<!-- 片元着色器 -->
<script id="fragmentShader" type="x-shader/x-fragment">
    precision mediump float;
    uniform bool u_IsPOINTS;
    void main(){
      if(u_IsPOINTS){
        float dist=distance(gl_PointCoord,vec2(0.5,0.5));
        if(dist<0.5){
          gl_FragColor=vec4(1,1,0,1);
        }else{
          discard;
        }
      }else{
        gl_FragColor=vec4(1,1,0,1);
      }
    }
  </script>
<script type="module">
  import { initShaders, getMousePosInWebgl } from "../jsm/Utils.js";
  import Poly from '../jsm/Poly.js';

  const canvas = document.querySelector("#canvas");
  canvas.width = window.innerWidth;
  canvas.height = window.innerHeight;

  // 获取着色器文本
  const vsSource = document.querySelector("#vertexShader").innerText;
  const fsSource = document.querySelector("#fragmentShader").innerText;

  //三维画笔
  const gl = canvas.getContext("webgl");

  //初始化着色器
  initShaders(gl, vsSource, fsSource);


  //声明颜色 rgba
  gl.clearColor(0, 0, 0, 1);
  //刷底色
  gl.clear(gl.COLOR_BUFFER_BIT);

  const poly = new Poly({
    gl,
    circleDot: true,
    types: ['POINTS', 'LINE_STRIP']
  })

  canvas.addEventListener('mousedown', (event) => {
    const { x, y } = getMousePosInWebgl(event, canvas)
    poly.addVertice(x, y)
    gl.clear(gl.COLOR_BUFFER_BIT);
    poly.draw()
  })


</script>
</body>

</html>
